In a multi-cylinder engine having a plurality of cylinders, air is introduced from the outside via an air cleaner box or the like. The air introduced through the air cleaner box or the like, or a mixture of fuel and air (hereinafter, simply referred to as a gas) is distributed to each of the cylinders via an intake passage. The filling amount of the gas in each of the cylinders changes according to a temperature of the gas. That is, the air-fuel ratio changes depending on the temperature of the gas. Therefore, there is a possibility that combustion in the cylinder may be adversely affected by such a change in the air-fuel ratio.
Patent Document 1 describes a V-type multi-cylinder engine in which supplied air compressed by a supercharger is cooled by an intercooler and then filled into each of cylinders. In the case of the multi-cylinder engine disclosed in Patent Document 1, the temperature of the supplied air is detected, and the amount of coolant flowing into the intercooler is increased or decreased according to the detected temperature of the supplied air. In Patent Document 1, the temperature of the air is kept constant by increasing or decreasing the amount of the coolant as described above, and thus the change in the air-fuel ratio is suppressed.